Polymer micro-particles in the recent years have been used to modify polymers, as additives in cosmetics and pharmaceutical agents, and as rheology modifying agents in paint and the like since the particle size is small, surface area is very large and the dispersion properties in other substances are good. Polymer micro-particles attracted attention particularly as starting materials for resin molding technology such as rapid prototyping wherein custom made molded products are manufactured by combining the polymer micro-particles with laser processing technology.
Micro-beads manufacturing processes can be roughly divided into two types. One process is the built up method wherein micro-beads of a set size are formed from small shapes or shapeless solutions and the like. A typical example is a method in which micro-beads are formed using polymerization steps such as emulsion polymerization and suspension polymerization. In addition, processes such as spray dry methods and atomizing (sprays) methods (for example, the one disclosed in JP 2008-169275) may also be used. Such processes use solvents and additives, and complete removal of such solvents and the like from the micro-beads formed is difficult to achieve. In addition, only the polymers that are suited to such polymerization processes, solvents and the like can be used, and the usable polymer itself is limited.
The other process is the breakdown method wherein micro-beads of set size are formed from large shapes, typically using a grinding process. The grinding process is used to form microparticles by combining a compression shear type mill, roller mill and the like and a sorting device. However, the process has problems. For example, the polymer that can be used is restricted, the micro-particle formation efficiency is poor for the enormous amount of mechanical energy consumed and only micro-particles with poor sphericity are formed.
The present invention is a means to produce micro-beads having an average particle size of from several microns to nanometers using filaments with a set diameter (for example, from 100 μm to 200 μm). Therefore, the micro-beads manufacturing means of the present invention is one type of breakdown method and presents a completely new means previously unknown. A filament drawing technology using infrared beams was disclosed in a previous patent application filed by the present inventors (International Disclosure Publication WO2008/084797A1). The present invention further develops the technology of the previous invention and presents a means to effectively form micro-beads comprising thermoplastic polymer micro-particles.